<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>标题</title>
    <link rel="stylesheet" href="../css/bootstrap.min.css">
</head>
<body>
<center>
    <h1>标题一<small>小标题</small></h1>
    <h2>标题二</h2>
    <h3>标题三</h3>
    <h4>标题四</h4>
    <h5>标题五</h5>
    <h6>标题六</h6>

    <span class="h1">标题一</span><!-- 36px -->
    <span class="h2">标题二</span><!-- 30px -->
    <span class="h3">标题三</span><!-- 24px -->
    <span class="h4">标题四</span><!-- 18px -->
    <span class="h5">标题五</span><!-- 15px -->
    <span class="h6">标题六</span><!-- 12px -->
</center>

</body>
</html>